An analog to digital count is a number produced by an analog-to-digital converter to measure a physical quantity. The measurement action counts the time for the measurement transducer to reach equilibrium. A count represents a quantity kind that depends upon the analog process that is being measured. For this reason, the association between count and quantity kind should ideally not be fully specified in this ontology, but should wait until the time of describing a particular device. However, that specification may require additional syntax in a schema. The current strategy in this ontology is to leave the specification of quantity kind to the point of description of a device, and to expect the additional syntax in the schema that uses this concept. The alternative is to define a subclass of AToDCount for each quantity kind. The delayed specification of quantity kind may provide a model to simplify the definition of other units. Typically, a count will be the basis for a conversion-based unit that converts the count into a physical quantity.
Acoustic power measures the energy of sound in matter.
The amount of a substance is correlated with the number of molecules of that substance that are present.
An ampere is one of the base units in the SI units of measure, corresonding to the quantity kind of electric current. It represents a coulomb of electrical charge flowing through a known cross section per time. The default interpretation of cross section is the cross section of a wire in an electrical circuit, perpendicular to the path of the wire. For current through other media, the cross section must be explained separately.
An ampere-hour is a measure of electric charge typically used to describe the capacity of an electric battery.
Angle measures the arc separation of two rays at some standard radius from their common point of origin. There is a choice between two angles, each of which is the difference between a full revolution and the other.
An angular rate is a measure of speed of rotation.
An arcsecond is 1/3600 of a degree of angle.
Astronomical magnitude provides a logarithmic comparison of apparent magnitudes of stars and other visible objects.
An astronomical unit is the nominal distance between Earth and Sun.
A bar is approximately the same a the air pressure on Earth at sea level.
A bit is a measure of information, uncertainty, or entropy.
A candela is the unit of luminous intensity in the international system of units.
Capacitance is the amount of charge that can be stored in a capacitor per change in electrical potential across the input to the device.
A count is an integer that represents the number of individuals of the subject class.
Data rate quantity kind is the rate of transfer of information per time.
A day is the nominal time for the Earth to rotate from one noon to the next noon at the same geographic location.
A decibel is 10 times the base 10 logarithm of the ratio of a measured quantity to a reference quantity. The quantities are generally power or intensity. The reference quantity is often implicit in casual usage. In this ontology, the implicit form only refers to the sound pressure level reference near the threshold of human hearing, the sound of a mosquito flying three metres away. All other reference quantities must be stated in the name of the unit, such as dBW, in which the reference quantity is one Watt.
A decibel watt is 10 times the base 10 logarithm of the ratio of a measured quantity to 1 watt.
A degree of angle is 1/360 of one full rotation.
Electric current density is the same as electric current, but normalized per cross section area through which the current flow.
Electric current is a measure of the amount of electrical charge flowing through a known cross section per time. The default interpretation of cross section is the cross section of a wire in an electrical circuit, perpendicular to the path of the wire. For current through other media, the cross section must be explained separately.
An electric potential gradient can be used to estimate the chance of dielectric failure. This quantity kind is also known as electric field strength.
Electric potential measures the energy that would be gained by an electric charge moving from the point of measurement to the reference point, which has zero potential.
An electron is an elementary particle that carries an electric charge. The unit of electron is the measure of the charge of one electron.
Entropy may also be called "heat capacity".
A farad is the charge in Coulombs that a capacitor will accept for the potential across it to change by one volt.
A frame count represents the quantity of frames that have been imaged by a camera.
Frequency measures the rate at which some implicitly defined event occurs. This ontology differentiates inverse seconds from frequency, because the former has no event associated with it.
Hertz is the frequency of 1 event per second. The event is not explicitly defined in the unit.
John von Neumann's advice to Claude Shannon about using the term "entropy" also carred the reason that "no one knows what entropy really is, so in a debate you will always have the advantage".
This quantity kind is also known as entropy. Claude Shannon is said to have considered calling it information or uncertainty, preferring the latter because the former seemed overused. John von Neumann advised calling it entropy, because it was already in use in statistical mechanics.
Luminance provides a measure of spectral flux density that is invariant along a light beam.
Luminosity, or luminous intensity, measures the strength of electromagnetic radiation.
A mole is a base unit in the SI units of measure. It represents the quantity of a molecular species.
A nit is a measure of luminance, which is invariant along the propagation of a light beam. It is measured in candelas per square meter.
The pixel unit represents a count of 1 pixels.
The pixel quantity kind represents a count of pixels.
The number of countable individuals of the subject class.
A radian is a natural measure of angle. It is the ratio of the length of the arc within the angle to the length of the radius of the arc. There are 2pi radians in a full rotation. In SI units a radian would be unitless, because it is the ratio of two lengths. In this ontology it is treated as a fundamental concept, independent of interaction with length.
A radian per second is an angular rate that rotates one radian each second of time.
Stellar magnitude provides a logarithmic scale for describing the brightness of stars in which the star Vega has magnitude zero, and dimmer stars have higher magnitudes.
Torque has the same units as energy, which is a different quantity kind.
A volt is the unit of energy gained by one coulomb of electrical charge moving from the point of measurement to the reference point, where the potential energy is zero.
Volumetric flow measures the rate of passage of incompressible fluid through a portal, or the rate of sweep of space by a moving scoop.
A weber per square metre is also known as a tesla.
Energy is also known as work and quantity of heat. Energy has the same units as torque, which is a different quantity kind.